With the Rocket Steelhead Mechanical broadhead I tie the blades down with Dental Floss when I want to practice with my vertical bow.
This keeps the blades from opening, and getting damaged or dulled.
With ten wraps of floss knotted several times between the wraps they will last several shots.
My arrows fly 268 fps, weigh 420 grains, and that amounts to 67 ft-lb of KE.
The dental floss doesn't even last one shot with the Tac15.
I'm going to have to look at using rigging wire.